Signaling device for scoring gunnery target practice



Nov. 24, 1964 J. A. 1. OHLUND ETAL 3,153,372

SIGNALING DEVICE FOR SCORING GUNNERY TARGET PRACTICE Filed Feb. 16, 1962 2 Sheets-Sheet 1 W JaZm Alzxfngvar UZ-Juni Karlfiagnar .Anderssan 3! 5 sllgard Nov. 24, 1964 J. A. l. OHLUND ETAL 3,158,372

SIGNALING DEVICE FOR SCORING GUNNERY TARGET PRACTICE Filed Feb. 16, 1962 2 Sheets-Sheet 2 JMJMH7M Jahn Alsxfngvar UZ-LZ-und ,K'arZRa narAnderssan t-mar MW/ A 35 5% lam 1.15142522575170 United States Patent 3,158,372 SEGNALENG DEVECE FUR SQGRENG TARGET PRACTECE iohn Alex Ingvar Ghlund, Huskvarna, and Karl Ragnar Andersson and Gunnar Alexius Waligard, Joplin-ping, Sweden, assigncrs to Svenska Aeroplan Alttiebolaget, Linlroping, Sweden, a corporation of Eweden Filed Feb. 16, 1962, Ser. No. 173,636 Claims priority, application Sweden Feb. 20, 1961 ll Qlaims. (Cl. 273l02.

This invention relates to devices for scoring accuracy of aim during gunnery target practice, and refers more particularly to a device of the class which generates electrical signals that can be transmitted to a recorder or indicator for providing indications of the accuracy of the gunners aim during tar et firing.

While useful in other types of target shooting, devices of this type have particular utility in connection with airto-ground gunnery practice, since they make it possible to apprise the gunner of the results he has achieved almost immediately after he has fired, and while he is still fully cognizant of the position and attitude he maintained at the time of firing. In all types of gunnery work a device of the character described has the advantage of making it unnecessary to visually inspect the target for the purpose of scoring the gunners results.

A device of the general type here under consideration is disclosed in British Patent No. 652,032, and it is also known to employ radar apparatus for obtaining substantially instantaneous recordings or indications of gunnery practice results.

In practice, however, it has been found that prior devices of the character described exhibit some discrepancy between the number of hits scored by the apparatus and the nurnber of rounds actually striking the target. These discrepancies have been relatively largest when the number of shots scored has been small. for the inaccuracy of such prior devices has been their responsiveness to near misses as Well as to actual hits on the target.

By contrast, it is a general object of this invention to provide a target gunnery scoring device of the character described which is capable of recording those rounds that actually strike the target but is unaffected by near misses, and which therefore produces a high degree of consistency between the scores recorded by the device and the results actually achieved by the gunner.

More specifically, it is an object of this invention to provide a gunnery target practice device of the type which emits an electrical impulse signal each time a hit .is achieved on a target, which device is substantially unaffected by air pressure shock Waves from passing projectiles that do not hit the target, and is also capable of discriminating between actual hits on the target and dirt thrown against the target by projectiles impacting near it.

Another object of the present inventionris to provide a signal generating device for gunnery target practice, adapted for use with known indicating and recording devices, by which electrical signals are emitted in response to the striking of a target by a projectile, and which is capable of producing signals that can be used by known apparatus to define the particular zone within the target area in which a projectile has struck.

These objectives are achieved in the device of the pres- GUNNERY ent invention by providing a target plate of substantially rigid vibration transmitting material, intended to be hit by properly placed shots, to which is secured a directional, vibration sensitive transducer or signal transmitter, wherein the transducer is so arranged that it emits an electrical impulse signal only when the target plate is struck by a projectile and as a result of the vibration One reason- With the above and other objects in View which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiments of the invention herein disclosed may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a front perspective view of a device for indicating results during gunnery target practice embodying the principles of this invention;

FIGURE 2 is a sectional view on an enlarged scale of a portion of the device shown in FIGURE 1;

FIGURE 3 is a longitudinal sectional view of the signal transmitter or transducer of the device;

FIGURE 4 is a more or less diagramamtic fragmentary view in elevation of a modified embodiment of the invention;

FIGURE 5 is a front perspective view of another modified embodiment of the invention; and

FIGURE 6 is an elevation view of still another modified embodiment of the invention.

Referring now to the accompanying drawings, the numeral 5 designates generally the novel signal generating device of this invention which comprises in general a target plate 6 that defines an area at which shots are to be directed during gunnery practice, and a transducer 7 secured to the targetplate and connectable, by means of a cable 8, with a recording or indicating device R of known construction. The purpose of the signal generating device is, of course, to transmit an electrical impulse to the recorder R each time a projectile strikes the target plate.

The target plate 6 can be of any desired size and shape, and is formed of a substantially hard and rigid material having good sound conducting capacity such as Masonite. A frame 9 mounted on a stand It) supports the target plate in any desired position of use. The frame is substantially wider and higher than the target plate, and the latter is secured to the frame, with its edges spaced therefrom, by means of strips 11 of rubber cloth or similar resilient material having good vibration insulating characteristics so that the target plate is suspended from the frame in a manner permitting thev plate to have damped bodily motion, and insulating the plate from ground vibrations that may be transmitted to the frame.

When a projectile strikes the target plate, the electrical signal transmitted to the recorder R is generated by the transducer or signal transmitter '7. As best seen in FIG URES 2 and 3, the transducerjcomprises a rigid airtight housing 12 across which, extends a vibration sensitive diaphragm 13 and in which is mounted a permanent magnet 14 that has its pole pieces 15 and 16 embraced by coils 1'7 and 18. It will be apparent that the transducer is of the electro-dynamic type,

wherein the diaphragm is of magnetically permeable ma- 1 The diaphragm 13 has a mass load 22 which gives it substantial inertia so as to render it responsive to the vibrations of the housing along an axis perpendicular to the diaphragm. Layers 23 or" self-damping material on the diaphragm provide it with suitable frequency characteristics. The housing or casing 12; is airtight, so that the diaphragm cannot be affected by air pressure waves from projectiles which pass near the transducer. Since the diaphragm extends across the housing and in effect divides it into two compartments, the diaphragm has air holes 25 therein through which air can pass as it vibrates.

The transducer is secured to a beveled corner portion of the target plate s by means of a rigid fastening element 26 and a rigid sleeve 27 which connects the fastening element with the transducer housing 12. Obviously the fastening element could comprise a part of the housing if desired, theimportant consideration being securement of the transducer to an edge portion of the target plate in such a manner that edgewise vibration of the target plate is transferred to the transducer housing. To this end the fastening element 25 is bifurcated by axial slot 25' that opens to one end thereof and in which the marginal edge portion of the target plate is snugly received. A screw 28 is threaded into the fastening element at an oblique angle to the face of the target plate such that as the screw is tightened it forces the edge of the plate tightly against the bottom of the slot 2-5.

The fastening element holds the transducer with its diaphragm substantially perpendicular to the plane of the target plate and substantially parallel to an edge of the plate adjacent to the transducer. Since the transducer is responsive to vibrations imparted to'the housing in the direction of its axis, and is substantially nonresponsive to vibration shocks parallel to its diaphragm, the transducer is highly directional and has its axis of sensitivity within the target plate as a result of the mounting just described.

The described manner of mounting the transducer, together with its enclosure in the airtight housing 12, renders it nonresponsive to near misses.

A shock wave due to a projectile passing the target plate without striking it can be divided into two velocity cornponents, one parallel to the plate and one normal to it.

The parallel component washes over the plate without emitting any appreciable energy, while the component normal to the plate causes oscillation of the plate normal to its plane. The magnitude of such oscillations varies with the size of the target plate, but since such oscillations take place in directions substantially transverse to the axis of sensitivity of the transducer, they afiect the transducer only very slightly.

However, a projectile which strikes and penetrates the target plate forces the plate material edgewise outwardly, in all directions, propagating an edgewise moving shock wave through the plate which travels therethrough at the velocity at which sound is conducted by the plate material and which of course vibrates the transducer housing 12 along its axis of sensitivity to effect relative motion of the diaphragm and thus produce an electrical impulse signal.

The location of the transducer on a beveled corner of the target plate as shown disposes the sensitivity axis of the transducer in an arbitrarily chosen direction within the plane of the target plate.

Preferably a layer 30 of soft vibration, damping material such as felt, polyurethane foam or the like is bonded to the front face of the target plate. This insulation facing tends to further decrease the eifect upon the transducer of shock waves due to near misses, and prevents the device from scoring a hit when stones or dirt are thrown against the target plate by a projectile impacting in front of it. The insulation layer also has the desirable effect of damping the inherent oscillations of the target plate so that the device can discriminate individual shots hitting the plate in rapid sequence, t us allowing the calculating speed of the recorder to be maintained at a high level.

To protect the transducer, the cable adjacent to it, and the frame, armor plate 31 is mounted in front of these parts, as shown in FIGURE 2.

T he embodiment of the invention show in FIGURE 4 is capable of emitting signals corresponding not only to hits made on the target but also to the particular zone within the target area in which each hit was made. In this case the target plate is built up of a number of plates 32, each corresponding generally to the target plate 6 of the previously described version of the invention, but the several plates 32 are supported in vibration insulating, spaced apart, coplanar relation to one another and are connected by strips 33 of rubber cloth or the like. Each of the plates 32 has a transducer 7 secured thereto, and a signal indicating a hit is emitted only by the transducer on the particular plate 32 that is actually struck by a projectile.

Another means for defining the specific zone within the target in which a hit is made is illustrated in FIGURE 5, wherein there are two parallel target plates 35 and 36, mounted one in front of the other, each having a transducer 7 mounted thereon as in the FIGURE 1 embodiment. However, the front target plate 35 has a central hole 3'? therein, and therefore projectiles passing through this hole and striking the rear target plate will cause only the transducer on the rear target plate to emit a signal. Projectiles hitting within the target zone but outside the bulls-eye represented by the hole 37 will of course strike both plates, causing both transducers to emit signals.

The embodiment of the invention illustrated in FIGURE 6 affords another means of scoring the specific zone within the target area in which a hit is made. case a single target plate in the shape of a tank is mounted on supporting stakes 33 by means of vibration dampers 35 of rubber or the like. Three transducers 4t 41 and 42 are secured to the target plate, at spaced apart locations around its edge portion, with their axes of sensitivity extending into the target plate at different angles. The three transducers are adapted to be connected with a recording apparatus of known type which is capable of detecting and indicating the time difference between the respective signals emitted by them.

A shot hitting the target plate at the point ed, for example, will propagate a shock wave that will travel edgewise in all directions through the target plate, at

unif rm velocity, and which will thus first affect the The target plate can thus be nearest transducer 41. divided by a. pair of lines, each equidistant along its length from a pair of transducers, into three zones A, B and C. The shot hitting the target at point 44 will be scored in zone B because that point is closest to transducer 41, the transducer that emitted the first signal.

From the foregoing description taken together with the accompanying drawings, it will be apparent that this-invention provides a simple and relatively inexpensive device for indicating accuracy of aim during gunnery target practice, which produces electrical impulse signals in response to shots actually hitting the target, and which very effectively discriminates against near missess, and

which, moreover, can be employed to score the particular zone within a target area in which a projectile'strikes.

What is claimed as our invention is:

1. In a device for producing signals that can be used to obtain indications of accuracy of aim during target practice: a target plate of substantially rigid vibration transmitting material, defining an area in which shots are to be placed; means for supporting the target plate inresponsivetransducer for generating an electrical signal in response to a vibration impulse along one axis of the transducer, and which is substantially nonresponsive to vibration impulses along other axes; and rigid vibration transmitting means securing the transducer to an edge portion of the target plate with the transducerso oriented that its said one axis is parallel to the planeof the target In this plate, so that the transducer produces an electrical signal only when a projectile strikes the target plate and thereby propagates an edgewise traveling shock wave therethrough, and so that the transducer is nonresponsive to vibrations normal to the plane of the target plate, such as those due to air shock waves from projectiles that pass near the target plate without striking it.

2. The device of claim 1, further characterized by a layer of substantially soft vibration damping material overlying one face of the target plate, at the side thereof from which projectiles are to be shot at the plate.

3. The device of claim 1, further characterized by a second directional transducer; and vibration transmitting means securing said second directional transducer to another edge portion of the target plate, spaced from the first, and with the axis of sensitivity of said second transducer parallel to the plane of the target plate and substantially intersecting the axis of sensitivity of the first designated transducer within the area of the target plate, so that signals from the two transducers can be compared with one another to provide an indication of the portion of the target plate struck by a projectile.

4. The device of claim 1, further characterized by a second device duplicating the first but having a hole through its target plate, the target plate of said second device being mounted in front of that of the first and parallel thereto so that an accurately placed hit will be indicated by a signal from the transducer of the first device, coinciding with the absence of a signal from the transducer of the second device, indicating that the projectile making such hit has passed through said hole in the target plate of the second device.

5. The device of claim 1, further characterized by means defining an airtight enclosure for the transducer by which the same is rendered substantially nonresponsive to air pressure waves caused by projectiles passing near it.

6. In a device for indicating accuracy of aim during target practice: a directional transducer for producing an electrical signal in response to a vibration impulse along one axis of the transducer, and which is substantially nonresponsive to vibration impulses along the other axes; means providing an air tight enclosure for said transducer by which the same is rendered substantially non-responsive to air pressure waves; a target plate of vibration transmitting material; means mounting said target plate for damped bodily vibratory motion in all directions; and vibration transmitting means securing the transducer to an edge portion of the target plate with said axis of the transducer parallel to the plane of the target plate and within the area thereof, so that the transducer produces an electrical signal only when a projectile strikes the target plate and thereby propagates an edgewise traveling shock wave therethrough.

7. In a device for indicating accuracy of aim during gunnery target practice: means defining a housing; means providing a self-damping diaphragm having substantial mass and extending across a portion of the housing so as to be movable relative to the housing means in response to vibration of the housing means along an axis substantially normal to the diaphragm; electrical impulse generating means fixed to the housing means and cooperable with the diaphragm to generate an electrical impulse signal upon movement of the diaphragm relative to the housing means; a target plate of substantially rigid vibration transmitting material; and rigid means securing the housing means to the target plate with the diaphragm substantially perpendicular to the target plate and facing a substantial portion of its area so that a shock wave traveling edgewise through the target plate due to a projectile striking the same effects electrical impulse signal generating relative motion between the diaphragm and the housing means.

8. The device of claim 7, further characterized by the fact that the housing means provides an airtight enclosure for the diaphragm by which the latter is rendered substantially nonresponsive to air pressure waves due to projectiles passing near the housing means.

9. The device of claim 7, further characterized by means mounting the target plate for damped bodily vibratory motion.

10. The device of claim 7, further characterized by the fact that said electrical impulse signal generating means comprises a permanent magnet having a pair of opposite pole faces adjacent to the diaphragm, so that the diaphragm is within the magnetic field of the permanent magnet, and a winding embracing the permanent magnet and in which currents are adapted to be induced in con sequence of vibration of the diaphragm relative to the permanent magnet.

11. The device of claim .7, further characterized by a layer of vibration damping material overlying a face or" the target plate to render the device nonresponsive to impacts other than those of projectiles striking the target plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,743,929 Smith May 1, 1956 2,767,987 Klose Oct. 23, 1956 2,783,047 Faxen Feb. 26, 1957 2,819,084 Brown et 'al. Ian. 7, 1958 2,890,052 Burrell June 9, 1959 2,926,015 Edrich Feb. 23, 1960 

1. IN A DEVICE FOR PRODUCING SIGNALS THAT CAN BE USED TO OBTAIN INDICATIONS OF ACCURACY OF AIM DURING TARGET PRATICE: A TARGET PLATE OF SUBSTANTIALLY RIGID VIBRATION TRANSMITTING MATERIAL, DEFINING AN AREA IN WHICH SHOTS ARE TO BE PLACED; MEANS FOR SUPPORTING THE TARGET PLATE IN A POSITION NORMAL TO A LINE OF TARGET PRATICE FIRE, SAID SUPPORTING MEANS ENGAGING ONLY A SMALL PORTION OF THE TARGET PLATE SO AS TO PERMIT SHOCK WAVES TO TRAVEL UNIMPEDED THROUGH THE TARGET PLATE; A DIRECTIONAL VIBRATION RESPONSIVE TRANSDUCER FOR GENERATING AN ELECTRICAL SIGNAL IN RESPONSE TO A VIBRATION IMPULSE ALONG ONE AXIS OF THE TRANSDUCER, AND WHICH IS SUBSTANTIALLY NONRESPONSIVE TO VIBRATION IMPULSES ALONG OTHER AXES; AND RIGID VIBRATION TRANSMITTING MEANS SECURING THE TRANSDUCER TO AN EDGE PORTION OF THE TARGET PLATE WITH THE TRANSDUCER SO ORIENTED THAT ITS SAID ONE AXIS IS PARALLEL TO THE PLANE OF THE TARGET PLATE, SO THAT THE TRANSDUCER PRODUCES AN ELECTRICAL SIGNAL ONLY WHEN A PROJECTILE STRIKES THE TARGET PLATE AND THEREBY PROPAGATES AN EDGEWISE TRAVELING SHOCK WAVE THERETHROUGH, AND SO THAT THE TRANSDUCER IS NONRESPONSIVE TO VIBRATIONS NORMAL TO THE PLANE OF THE TARGET PLATE, SUCH AS THOSE DUE TO AIR SHOCK WAVES FROM PROJECTILES THAT PASS NEAR THE TARGET PLATE WITHOUT STRIKING IT. 